I have both a XP-Pen Artist 15.6 Pro Pen display Drawing Tablet and the current generation of the 12.9 iPad Pro and Apple Pencil. I got the Artist 15.6 Pro first and used it constantly before I got the iPad. Then I got the iPad and the Artist 15.6 Pro mostly goes unused these days unless I need to specifically use Photoshop or Illustrator.

The Apple Pencil is decidedly a better drawing experience than the P05R Pen on the Artist 15.6 Pro . It's more accurate, has absolutely no parallax, requires no calibration, it has a more intuitive pressure response curve, and the feel of the stylus point on the screen is better (this one point is more subjective, but is how I feel about it).

On top of that, the iPad's touch gestures are second to none. Pinch zoom and rotate works flawlessly 99% of the time in every drawing app I've used. On the XP-Pen Artist 15.6 Pro sometimes I have a great run and it works really well and then some days it's just total crap and all but useless. You also do not have to fret about drivers at all.

Then on top of all of that, the new XP-Pen Artist 15.6 Pro are certainly pretty light and slim but there is no way I would ever set one up in a coffee shop. It would be kind of absurd with the Artist 15.6 Pro , your laptop, the cables and power adapters, etc. The iPad on the other hand I have taken with me everywhere. Used it for hours on cross country flights. Used it sitting in a park. In bed, on the bus, etc etc. It's got a great battery life, is a self contained computing device. It is easily my favorite digital art device I have ever used.

The app I use most often is called Procreate. I super love it. They've done an amazing job of distilling the app down to just what you need and no clutter or over complicated BS. It's also only about $20.

If you get a XP-Pen Artist 15.6 Pro , you will need a computer to pair with but it should overall be a better option, however if you want the portability i would recommend the ipad pro (Or any mobile variant like a surface or android equivelant)

If all you plan on doing is drawing and painting then the iPad is perfect. If you have even a passing interest in pretty much anything else then an Artist 15.6 Pro is probably a better idea.

The main issue with the iPad is that you’re limited to iOS apps. There really aren’t any fully-featured animation or 3D modelling apps yet, but the Artist 15.6 Pro will work with practically any desktop software.

Ill just write a pros and cons list for you to read better:

XP-Pen Artist 15.6 Pro Screen Drawing TabletPros

Better for long drawing sessions

Higher res screen

no parallax

supports 60 degrees of tilt sensitivity

supports 8192 levels of pressure sensitivity

You get a cursor/crosshairs when hovering your pen above where drawing

Can be used to draw super demanding stuff if you have the pc to back it

Bigger and cheaper

Desktop applications can be used, which are mounds better than mobile.

Cons

Not support Multi-Touch Attribution

Not really portable at all, would be clunky to bring around

You cant bring it to class with you easily, which means you will have to export whatever you were working on if using a desktop, if you have a laptop this isnt really an issue.

It eats up space on your desk, and is somewhat of a hassle if you have restricted space.

Ipad pro 12.9"Pros

Easy to bring everywhere, a much easier task than bringing a laptop.

It can be a legit tablet as well, for all your browsing and computing needs

No wires restricting you, draw on your floor or couch if you feel like it

Standalone, so no need to hook up to a pc

Will def come color calibrated so no need to fiddle with that stuff

Cons

I personally think the drawing programs are garbage, but they might not be garbage for you. And animation? Probably worse... I recommend checking out programs before getting it.

Lower end processing power than if you paired the XP-Pen Artist 15.6 Pro with a powerful laptop/desktop, but shouldnt really be an issue if you work on reasonable resolutions.

Pricey, not to say the Wacom tablet isnt either

Overall

I think either should work out well for you, but if you need complex art i would personally recommend the XP-Pen Artist 15.6 Pro . Portability and ease of convinience goes to apple.

The reason that Artist 15.6 Pro / Ipad Pro has no parallax is that the screen is laminated. By laminated, I mean having the LCD panel & the glass in one piece, which lower the distance between the cursor & the pen tip (having such distance is the main culprit for parallax).

For the Ipad alternatives, i also suggest looking into, like the surface/android tablets.